Obviously much is still unknown about the religion and coronation systems. One shortcoming of the CK2 coronation system is that it did not acknowledge the Pope's attempts to extend Roman authority through coronation of pagan and non Catholic rulers. A great example is Daniel of Galicia who was crowned by a delegation from Pope Innocent IV as part of a transactional deal that also involved expectations of subordination of his territories to Rome on his part and the pope calling for a crusade against the Mongols on the part of the pope (neither of these latter two conditions were actually realized though). I believe that some kings of Serbia were possibly also crowned by the Pope despite not follwoing Catholic rite or acknowledging papal supremacy. I believe some late antiquity coronations of tribal rulers were concurrent with or followed shortly after conversion.
Tl;dr If Catholic moral authority or its equivalent is high and the pope (or other pope tier religious figure?) is nearby, I think it would be cool if this kind of interaction might be possible in CK3. Maybe you get a favor-equivalent from the pope but antagonize clergy / zealous of your religion.
Tl;dr If Catholic moral authority or its equivalent is high and the pope (or other pope tier religious figure?) is nearby, I think it would be cool if this kind of interaction might be possible in CK3. Maybe you get a favor-equivalent from the pope but antagonize clergy / zealous of your religion.